Articles having structured surfaces, and processes for providing such articles are known. In the case of optical articles, see, for example, U.S. Pat. Nos. 6,096,247 and 6,808,658, and published application U.S. 2002/0154406 A1. The structured surfaces disclosed in these references include microprisms (such as microcubes) and lenses. Typically these structures are created on the surface of a suitable polymer by, for example, embossing, extrusion or machining.
The manufacture of such articles often comprises a step in which a tool bearing a negative version of the desired structured surface is contacted with a polymer resin. Contact with the resin is maintained for a time and under conditions adequate to fill the cavities in the tool after which the resin is removed from the tool. The resulting structured surface is a replicate of the negative surface of the tool.
Birefringent articles having structured surfaces are also known. See, for example, U.S. Pat. Nos. 3,213,753; 4,446,305; 4,520,189; 4,521,588; 4,525,413; 4,799,131; 5,056,030; 5,175,030 and published applications WO 2003/0058383 A1 and WO 2004/062904 A1.
Processes for manufacturing stretched films are also known. Such processes are typically employed to improve the mechanical and physical properties of the film. These processes include biaxial stretching techniques and uniaxial stretching techniques. See for example PCT WO 00/29197, U.S. Pat. Nos. 2,618,012; 2,988,772; 3,502,766; 3,807,004; 3,890,421; 4,330,499; 4,434,128; 4,349,500; 4,525,317 and 4,853,602. See also U.S. Pat. Nos. 4,862,564; 5,826,314; 5,882,774; 5,962,114 and 5,965,247. See also Japanese Unexamined Patent Publications Hei 5-11114; 5-288931; 5-288932; 6-27321 and 6-34815. Still other Japanese Unexamined Applications that disclose processes for stretching films include Hei 5-241021; 6-51116; 6-51119; and 5-11113. See also WO 2002/096622 A1.